Hybrid Power Comes to Aviation

OSHKOSH, Wisconsin — Amid all the talk about electric airplanes here, one company has developed a hybrid motor for airplanes as an intermediate step to all-electric aircraft. German planemaker Flight Design is testing a hybrid that’s very similar to the hybrid-car concept, with added safety benefits that can be utilized by airplanes.

Like cars, aircraft need the most power to get going, take off and climb. Planes need much less power for cruising. Flight Design’s engine uses a 40-hp electric motor directly connected to a normal gasoline-burning 115-hp Rotax 914 airplane engine via belt drive to provide about five minutes of boost power.

The pilot pushes the single power lever forward for takeoff, and both motors are running to provide the equivalent of a 160-hp engine. Once the four-seat airplane is at altitude, the pilot reduces power for cruise and the electric engine is no longer delivering power. This leaves a 115-hp gasoline engine to provide the cruise power, which is more efficient than the 160-hp engine the hybrid system replaces.

Like its car cousin, the aircraft engine can also use regenerative braking. When a pilot reduces power for descent, the windmilling propeller is used to recharge the battery pack for the next flight.

Flight Design’s Oliver Reinhardt told Wired.com the hybrid has a built-in safety backup. “If the gasoline engine were to quit,” he said, mentioning every pilot’s nightmare, “the electric motor could also be used to stretch the glide.” This would give a pilot more time to find a suitable landing spot or troubleshoot the problem.

Reinhardt says the engine was produced to power a new aircraft currently being developed by Flight Design. He says with an all-new aircraft, they wanted a new power plant. “What we have available on the market, the current engines, are based on technologies from the ’30s and ’40s,” Reinhardt explained to Wired.com. “We must have a proper engine that is fuel-efficient, that is noise-efficient and is economically viable.”

Reinhardt believes the hybrid system not only increases efficiency, it also provides important information that will help further develop electric airplanes larger than the ultralights many manufacturers are building. “You gain much more experience in operating the electrical part of it for an all-electric airplane.”